• 专利附录
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  • 权利要求
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    • 专利摘要:
    Procedure for obtaining in situ thermal fluids containing sub-micron thermoregulatory particles. The present invention refers to a process for obtaining in situ low viscosity thermal fluids containing sub-micron thermoregulatory particles, encapsulating organic phase change materials (PCMs) of different melting points and with thermal reversibility. The thermal fluid obtained can be used as a transport and storage system for thermal energy, in thermal solar collectors, photovoltaic and thermal hybrid solar collectors or as an additive in the production of thermoregulatory building materials. (Machine-translation by Google Translate, not legally binding)
    公开号:ES2804063A1
    申请号:ES201930715
    申请日:2019-07-31
    公开日:2021-02-02
    发明作者:Franco Manuel Carmona；Romero Juan Francisco Rodriguez；Simon Ana Maria Borrego；Saenz Ignacio Garrido；Mellado Francisco Javier Ramos；Pedrajas Daniel Lopez；Vazquez Macarena Jimenez
    申请人:Universidad de Castilla La Mancha；
    IPC主号:
    专利说明:

    [0001] PROCEDURE FOR OBTAINING IN SITU OF THERMAL FLUIDS CONTAINING
    [0003] FIELD OF THE INVENTION
    [0005] The present invention belongs to the technical field of suspensions for the transport of heat and, more specifically, to suspensions that include a thermal fluid and a phase change material (PCM).
    [0007] BACKGROUND OF THE INVENTION
    [0009] At present, methods are known to improve the performance of heat transfer fluids, by joining a heat transfer fluid and a phase change material (PCM).
    [0011] Phase change materials (PCM) are characterized by being chemical compounds that when undergoing a phase transition accumulate or release a large amount of energy in the form of latent heat (enthalpy), assuming a reversible heat storage and thus making the temperature of a system can be kept constant for long periods of time. In addition, they are interesting materials for numerous applications because they also have other properties such as high thermal conductivity, chemical stability, low cost, and they are not corrosive or toxic.
    [0013] The introduction of the phase change material into the heat transfer fluid leads to improved and highly reversible thermal transport properties at elevated temperatures, while ensuring low fluid viscosity at operating temperatures.
    [0015] There are some examples in the state of the art, such as patent US6447692B1, which describes a method to prepare a heat transfer fluid with improved thermal performance, by incorporating nanometric capsules with polymeric shells of organometallic or block copolymers, with characteristics hydrophilic or hydrophobic, produced using ethylene oxide and propylene oxide and based on polypropylene and polystyrene, respectively.
    [0017] These shells contain the phase change material which are mainly fatty acids, acetamide or glycols. These nanocapsules, once they have been produced and dried, are dispersed in the base heat transfer fluid (commercial products, different from U zan or surac an es water and achieves o n os e nanoc psuas in euo rmco of up to 30% v / v. Considering the application temperatures, they appear to be suitable for cooling systems, although they can go up to 80 ° C. However, among the claimed applications of this product, its possible use as a cooling fluid in PV / T hybrid solar collector systems does not figure.
    [0019] WO2013182713 describes a thermal fluid comprising a base thermal fluid and a phase change material. This fluid is obtained by a process that comprises dispersing or dissolving the encapsulated or non-encapsulated phase change material by (a) mechanical homogenization or (b) by sonic homogenization.
    [0021] Said document describes the use of the thermal fluid obtained as a transport system for thermal energy and with the capacity to store energy by combining the latent heat given by the phase change material in various applications such as parabolic-trough thermal collectors.
    [0023] As in the previous case, the production of the thermal fluid is carried out by mixing, with microcapsule concentrations of up to 30% w / w. The polymeric casings are made of silicon oxides and whose particle size can reach 10 mm.
    [0025] US6063312 describes a method and a composition of a heat transfer fluid comprising a carrier liquid (polyalphaolefin), a phase change material (polyoxyethylene stearate, polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyethylene glycol, a mixture of polyethylene glycols, a mixture of a polyethylene glycol and water, or mixtures) insoluble in the carrier liquid and a solid microporous structure (amorphous silica, a zeolite, a crystalline aluminophosphate, an aluminosilicate, or mixtures). According to the method of the invention, said phase change material is encapsulated in the solid microporous structure and subsequently mixed with said carrier liquid. The method of obtaining this fluid is by mixing, using the mother liquor as the base thermal fluid.
    [0027] WO81 / 02163 describes the production of a thermal fluid formed by metallic microcapules containing the phase change material (fatty acids and some inorganic substances) and in which the base thermal fluid fills the space between the particles. The microcapsules are spherical and have a size that is far from being submicron, being in the range of 10 to 1000 mm. Furthermore, this fluid being made up of metallic material can hardly be pumped.
    [0028] n em argo, nnguno e os os ocumen and is aoe are escr pro ea ucc n nto and a thermal fluid with high thermal storage capacity, also possess improved properties such as the ability to be pumped.
    [0030] DESCRIPTION OF THE INVENTION
    [0032] The present invention solves the problems present in the state of the art by producing a thermal fluid in situ , avoiding previous steps such as the separation of the reaction medium, the drying process and possible ruptures of the nanocapsules as a result of the reaction. dispersion in the base thermal fluid.
    [0034] Furthermore, the present invention claims the production of a thermal fluid with high pumpability as it has a dynamic viscosity close to that of water and with solid material contents of up to 40% w / w.
    [0036] A first aspect of the invention is a process for obtaining thermal fluids containing sub-micron thermoregulatory particles, which is carried out through the following steps:
    [0037] a) adding at least one molten organic phase change material to a reactor containing a mixture of water and at least one surfactant;
    [0038] b) emulsifying the mixture from stage a) by mechanical stirring at a speed of 1000-2000 rpm and ultrasonication for times between 10 min and 4 hours, c) maintaining the mixture from stage b) at a temperature higher than the melting point of the organic phase change material, obtaining an aqueous phase; d) preparing an organic phase by pre-polymerizing at least one monomer at a temperature between 40-80 ° C and stirring at a speed of 400-500 rpm; e) adding the organic phase obtained in step d) to the aqueous phase obtained in step c); Y
    [0039] f) stir at a speed of 1000-2000 rpm and at a temperature of between 60-80 ° C for 5 hours until the polymerization of the shell is complete.
    [0041] In another aspect of the invention, the surfactant is selected from the group comprising sodium dodecyl sulfate (SDS), gum arabic (GA), polyvinylpyrrolidone (PVP), sorbitan esters (Spans), polysorbates (Tweens), polyoxyethylene alkylphenols (tritrons). ) and / or their mixtures.
    [0043] In another aspect of the invention, the organic phase change material is selected from the group consisting of paraffins, fatty acids, or fatty acid mixtures.
    [0044] In another aspect of the invention, the monomer is selected from the group comprising styrene, divinyl benzene, methylmethacrylate, or melanin-formaldehyde.
    [0046] Another aspect of the invention is the use of the thermal fluid, obtained by the procedure described above, as a transport and storage system for thermal energy.
    [0048] Another aspect of the invention is the use of the thermal fluid, obtained by the procedure described above, in thermal solar collectors.
    [0050] Another aspect of the invention is the use of the thermal fluid, obtained by the procedure described above, as an additive in the production of thermoregulatory building materials.
    [0052] A final aspect of the invention is the use of the thermal fluid, obtained by the procedure described above, in photovoltaic and thermal hybrid solar collectors.
    [0054] DESCRIPTION OF REALIZATION MODES
    [0056] Having described the present invention, it is further illustrated by the following examples.
    [0058] Example 1. Procedure for obtaining a thermal fluid containing sub-micron thermoregulatory particles with a paraffin core and a vinyl shell
    [0060] Initially an aqueous phase was prepared, mixing in a reactor at least one surfactant of the following sodium dodecyl sulfate (SDS), acacia (GA) and polyvinylpyrrolidone (PVP), with water and molten paraffin as phase change material (PCM ) organic. The organic phase change material is added molten for proper homogenization and dispersion. The reactor is a jacketed reactor that operates at atmospheric pressure, inerted with a stream of pure N 2 and provided with a condensation system to avoid the loss of monomers.
    [0062] The aqueous phase was stirred at a temperature of 50 ° C and at a stirring speed between 1000-2000 rpm.
    [0063] erormen e, an organic mixture of mixed monomers was prepared, specifically styrene and divinylbenzene, in different mass proportions varying from 100/0, 75/25, 50/50, 25/75 and 0/100 .
    [0065] After mixing, 1% by weight with respect to the total amount of azobisisobutyronitrile monomers (AIBN) was added as the initiator of the reaction. This mixture was prepolymerized at 50 ° C, at an agitation of 400 rpm and for a time of 20-30 min.
    [0067] Once both phases had been prepared, the organic phase was slowly added to the aqueous phase, keeping the reactor stirring at 1500 rpm and the temperature at 80 ° C. The reaction was completed after about 5 hours and a thermal fluid containing sub-micron thermoregulatory particles was obtained as the product without any additional treatment.
    [0069] The main thermal and physical properties of the material obtained by the process of the present invention and a comparison with respect to commercial materials that may have similar applications are summarized below.
    [0071] Property definition
    [0072] - Carcass (%): the material type of the polymeric carcass is defined and the percentage by mass of the carcass with respect to the total solid particle is defined in parentheses;
    [0073] - wts%: percentage by mass of solids (polymer particles with encapsulated PCM) with respect to the total mass of the fluid;
    [0074] - TF: melting temperature of the phase change material;
    [0075] - AHF ( PCM): latent heat of fusion of the pure phase change material measured by DSC;
    [0076] - AH F (SO lido): latent heat of fusion of the solid particles contained in the slurry measured by DSC;
    [0077] - A H F ( liq): latent heat of fusion of slurry measured by DSC;
    [0078] - Tmax application: maximum temperature at which the solid particles contained in the fluid are stable;
    [0079] - g (25 ° C): dynamic viscosity at 25 ° C measured with a rotational viscometer;
    [0080] - Potential Z: stabilization potential of colloidal particles;
    [0081] - dn 0.5 : mean diameter of the fluid particles.
    [0083] In the study of the properties of the fluids obtained from the present invention, the following commercial paraffins from Rubitherm Technologies GmbH were used as phase change materials:
    [0084] -: eac n s reno vn enceno, oma Arabica Sodium dodecyl sulfate (GA + SDS) 40-60 with benzoyl peroxide (BPO).
    [0085] - RUBITHERM® RT27 (2): St / DVB ratio 25/75, GA + SDS 40-60 with azobisisobutyronitrile (AIBN).
    [0087] - RUBITHERM® RT27 (3): St / DVB 50/50, GA + SDS 40-60 ratio with BPO.
    [0089] - RUBITHERM® RT27 (4): Styrene / Methylmethacrylate (St / MMA) ratio 80/20, GA + SDS 40-60 with BPO.
    [0091] - RUBITHERM® RT50: St / DVB 25/75, GA + SDS 40-60 ratio with AIBN.
    [0093] - RUBITHERM® RT70 HC: St / DVB ratio 18.8 / 81.2, SDS + PVP 50-50 with AIBN.
    [0094] In the data obtained and reflected in table 1, it is observed that by means of the procedure described in this invention it is possible to produce thermal fluids that contain sub-micron thermoregulatory particles with paraffin core and polymeric shell different from that of the commercial materials MICRONAL® 5428 X, DS 5037 X and DS 5039 X from Microtek Laboratories Inc. (copolymers of styrene and divinylbenzene in this case, versus acrylic polymers for commercial materials), with similar solid concentration depending on the thermoregulatory capacity required in the final application and with different melting point. Specifically, no commercial materials have been found with melting points above 28 ° C.
    [0096] Regarding the stabilization potential of the colloidal particles (Potential Z), negative values were obtained, which indicates a high stability of the fluid.
    [0098] Table 1 shows how the commercial material is micrometric in size, while for the present invention the particles are nanometric in size (see mean diameter of the fluid particles (dn 0.5)). This difference increases its applicability since it makes it less susceptible to abrasion in pumping processes.
    [0100] On the other hand, in pumping processes the most important property is viscosity. The values found for the present invention are much lower or in the case of encapsulation of RT 70 at most, it is in the same range. A lower fluid viscosity is a great advantage since it significantly reduces pumping energy needs.
    [0101]
    [0102]
    [0103] The values of heat in in can a capacity of love guamen or rmco a cona and great thermal reversibility that these thermal fluids have with respect to the base liquid, without the need for a change in temperature and therefore, this additional advantage would grant many possibilities of use depending on the application temperature.
    [0105] Example 2. Procedure for obtaining a thermal fluid containing sub-micron thermoregulatory particles with a paraffin core and a Melamine-Formaldehyde (MF) copolymer shell
    [0107] Initially an aqueous phase was prepared by mixing in a reactor at least one surfactant of the following sodium dodecyl sulfate (SDS), acacia (GA) and polyvinylpyrrolidone (PVP), with water and molten paraffin as organic phase change material. The organic phase change material is added molten for proper homogenization and dispersion.
    [0109] The aqueous phase was stirred at a temperature of 50 ° C and at a stirring speed between 1000-2000 rpm.
    [0111] The reactor is a jacketed reactor that operates at atmospheric pressure, inerted with a stream of pure N 2 and provided with a condensation system to avoid the loss of monomers.
    [0113] Subsequently, an organic phase was prepared by mixing formaldehyde with melanin (2/3 of the total), in a melanin / formaldehyde molar ratio of 1/6. Once mixed, the pH value of the solution was adjusted between 8 and 9, with the help of triethanolamine. This mixture was heated to 70 ° C at 500 rpm stirring until the solution became clear.
    [0115] Once the previous solution had been prepared, it was completed with the addition of the melanin (remaining 1/3), maintaining heating and stirring.
    [0117] Once both phases had been prepared, the organic phase was slowly added to the aqueous phase, keeping the reactor stirring at 1500 rpm, at a pH between 4 and 6 with dilute sulfuric acid and the temperature at 60 ° C. The reaction was completed after about 5 hours and a thermal fluid containing submicron thermoregulatory particles was obtained as the product without any additional treatment.
    [0119] The main thermal and physical properties of the material obtained by the process of the present invention and a comparison with respect to commercial materials that may have similar applications are summarized below. The properties have been defined the same as in example 1.
    [0120] In this case, commercial paraffins from Rubitherm Technologies GmbH and high purity n-octadecane were used as phase change materials:
    [0121] - n-octadecane (1): Melamine / Formaldehyde (MF) molar ratio 1/6, n-octadecane / MF 60/40.
    [0123] - n-octadecane (2): Melamine / Formaldehyde (MF) molar ratio 1/6, n-octadecane / MF 80/20.
    [0125] - RUBITHERM® RT50: Melamine / Formaldehyde (MF) molar ratio 1/6, RT50 / MF 60/40.
    [0127] - RUBITHERM® RT70 HC: Molar ratio Melamine / Formaldehyde (MF) 1/6, RT70 / MF 65/35.
    [0129] Analogously to the previous case, in the present example it is demonstrated that fluids can be prepared with shell materials other than commercial acrylic polymers, more specifically with melamine-formaldehyde polymers. Likewise, all the considerations previously detailed for example 1 can be extrapolated to this second case (See Table 2).
    [0131] Latent heat values of commercial thermal fluids are not reported, although their solid particles are. It is observed that the solid particles of the thermal fluid object of the present innovation have a very similar latent heat, except the MICRONAL® 5428 X with a latent heat greater than 160 J / g. However, the thermal fluid reported with this product has a very high viscosity that limits its applications in pumping processes. This increase in viscosity may also be due to the large particle size (1000-5000 nm) of this commercial fluid compared to the sub-micron size (<225 nm) of the particles present in the thermal fluids considered in this innovation. Therefore, it is evident that the high latent heat, the rheological characteristics and the stability of the dispersion make the product object of the present innovation highly applicable in the field of thermal storage.
    [0133] According to the data obtained in the two examples, the process object of the present invention is considered very robust, since it allows the melting temperature of the encapsulated PCMs to vary within a wide range and stable and low-viscous fluids are obtained thanks to the submicron particle size.
    [0134]
    [0135]
    权利要求:
    Claims (8)
    [1]
    1. Procedure for obtaining in situ thermal fluids, characterized in that it comprises the following stages:
    a) adding at least one molten organic phase change material to a reactor containing a mixture of water and at least one surfactant;
    b) emulsifying the mixture from stage a) by mechanical stirring at a speed of 1000-2000 rpm and ultrasonication for times between 10 min and 4 hours, c) maintaining the mixture from stage b) at a temperature higher than the melting point of the organic phase change material, obtaining an aqueous phase; d) preparing an organic phase by pre-polymerizing at least one monomer at a temperature between 40-80 ° C and stirring at a speed of 400-500 rpm; e) adding the organic phase obtained in step d) to the aqueous phase obtained in step c); Y
    f) stir at a speed of 1000-2000 rpm and at a temperature between 60-80 ° C for 5 hours.
    [2]
    2. Process for obtaining in situ thermal fluids according to claim 1, wherein the surfactant is selected from the group comprising sodium dodecyl sulfate (SDS), gum arabic (GA), polyvinylpyrrolidone (PVP), sorbitan esters (Spans), polysorbates (Tweens), polyoxyethylene alkylphenols (tritrons) and / or their mixtures.
    [3]
    3. Process for obtaining in situ thermal fluids according to any of claims 1 to 2, wherein the organic phase change material is selected from the group comprising paraffins, fatty acids or fatty acid mixtures.
    [4]
    4. Process for obtaining in situ thermal fluids according to any of claims 1 to 3, wherein the monomer is selected from the group comprising styrene, divinyl benzene, methyl methacrylate or melanin-formaldehyde.
    [5]
    5. Use of the thermal fluid obtained by the process according to any of claims 1 to 4, as a transport and storage system for thermal energy.
    [6]
    6. Use of the thermal fluid obtained by the process according to any of claims 1 to 4, in thermal solar collectors.
    [7]
    7. Use of the thermal fluid obtained by the process according to any of claims 1 to 4 as an additive in the production of thermoregulatory building materials.
    [8]
    8. Use of the thermal fluid obtained by the process according to any of claims 1 to 4, in photovoltaic-thermal hybrid solar collectors.
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    同族专利:
    公开号 | 公开日
    ES2804063B2|2021-10-05|
    ES2804063B8|2021-10-06|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    WO2012110443A1|2011-02-16|2012-08-23|Basf Se|Microcapsules having a paraffin composition as a capsule core|
    CN109002090A|2018-07-06|2018-12-14|益文杰|A kind of host computer placing box|
    法律状态:
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